The present invention relates to gas turbine engines, and in particular, to starting of a gas turbine engine. In gas turbine engines with multiple spools, the engine is typically started by rotating a high spool and then lighting a combustor when the high spool reaches a suitable speed. In many gas turbine engines, a starter is used to rotate the high spool prior to lighting the combustor. After the combustor has been lit, the gas turbine engine can operate without assistance from the starter. A starter is typically not connected to a low spool, which is typically much larger than the high spool, has a substantially larger inertia than that of the high spool, and has a slower rotational speed than that of the high spool.
In some gas turbine engines, a motor/generator is connected to a gearbox, which is connected to the high spool. This motor/generator can be used as a starter motor to drive the gearbox to rotate the high spool for starting the gas turbine engine. Such an arrangement typically requires a relatively large gearbox connected to the high spool. This can be undesirable in applications where space is limited. Moreover, such an arrangement also limits the location and operation of the motor/generator.